(668g) Modeling Algal Cultivation in the United Arab Emirates

Authors: 
Gomez, J. A., Massachusetts Institute of Technology
Barton, P. I., Massachusetts Institute of Technology
Al Hajaj, A., Masdar Institute
Due to, first oil price volatility, and then climate change, Abu Dhabi has decided to become a worldwide leader in renewable sources of energy, sustainability, and carbon capture and sequestration (CCS). In 2006, Abu Dhabi launched the Masdar Initiative aimed at promoting the development and use of renewable sources of energy in Abu Dhabi [1]. This initiative includes the construction of Masdar City which will be a carbon-neutral city, the establishment of the Masdar Institute of Science and Technology, and the objective of increasing the share of renewables to at least 7% in Abu Dhabi’s power generation by 2020 [1]. This has resulted in Abu Dhabi establishing a nuclear program for civilian use and the largest solar energy farm [2]. Abu Dhabi has also launched an ambitious CCS project that will have captured five million tons of CO2 by 2012 [3], but there are concerns about the high cost of CCS. The main use of the sequestered carbon will be for Enhanced Oil Recovery (EOR), but Abu Dhabi is searching for other uses of this sequestered carbon. In addition, Abu Dhabi’s city council data indicates that 82 million gallons of wastewater are dumped directly to the sea causing harmful algae blooms in the ocean.

These situations present an outstanding opportunity for algal cultivation processes because of their ability to fix atmospheric CO2 and to remove nutrients from wastewater. Even more, biofuels and high value products can be obtained from algae reducing the cost of CCS. The United Arab Emirates (UAE) has a sizable potential for algal biofuels due to its vast desert expanses, long shorelines, year-round sunny days, availability of flue gas, seawater and wastewater, and native adapted algae species that tolerate salinity levels twice as high as those in the Gulf waters [2]. However, algal cultivation is challenging as it must be achieved in open ponds. Closed photobioreactors are not an option because they incur high capital and operating costs. Open pond systems have low biomass and lipids productivities because they are CO2 limited and they are susceptible to invasion by undesirable microorganisms. In order to increase productivity of open pond systems, reliable and predictive process models are needed.

Here, we use the high-rate algal bacterial pond (HRAP) [4], [5] model and dynamic flux balance analysis (DFBA) [6], [7] to model algal cultivation in the UAE. The model and ideas presented in [8] are taken as a start point. In this paper microbial consortia are used for two purposes. First, they increase culture resilience by utilizing resources more efficiently compared to an algae monoculture, making pond invasion by undesirable species more difficult [9]. Second, symbiotic relationships can be established between microalgae and other microbes in which the microbes convert carbon sources into CO2 and acetate, and algae converts the CO2 and acetate into biomass. Therefore, algae ponds can become feasible in locations far away from flue gas sources.

Here, we present the results of different case studies concerning the cultivation of algae in Abu Dhabi. In particular, we use experimental data regarding environmental conditions, wastewater composition, and flue gas composition to test different cultivation configurations and make predictions of novel system behavior [10], [7], [11]. 

References

[1]

D. Reiche, "Renewable Energy Policies in the Gulf countries: A case study of the carbon-neutral "Masdar City" in Abu Dhabi," Energy Policy, vol. 38, pp. 378-382, 2010.

[2]

A. A. Jaradat, "The current potential of algae biofuels in the United Arab Emirates," Biofuels, vol. 4, no. 4, pp. 347-349, 2013.

[3]

S. Nader, "Paths to a low-carbon economy - the Masdar example," Energy Procedia, vol. 1, pp. 3951-58, 2009.

[4]

H. Buhr and S. Miller, "A Dynamic Model of the High-Rate Algal-Bacterial Wastewater Treatment Pond," Water Res., vol. 17, pp. 29-37, 1983.

[5]

A. Yang, "Modeling and Evaluation of CO2 Supply and Utilization in Algal Ponds," Industrial & Engineering Chemistry Research, vol. 50, pp. 11181-11192, 2011.

[6]

A. Varma and B. Ø. Palsson, "Stoichiometric flux balance models quantitatively predict growth and metabolic by-product secretion in wild-type Escherichia coli W3110," Applied and Environmental Microbiology, vol. 60, no. 10, pp. 3724-3731, 1994.

[7]

R. Mahadevan, J. Edwards and F. I. Doyle, "Dynamic flux balance analysis of diauxic growth in Escherichia coli.," Biophysical Journal, vol. 83, no. 3, pp. 1331-40, 2002.

[8]

J. A. Gomez, K. Höffner and P. I. Barton, "From sugars to biodiesel using microalgae and yeast," Green Chemistry, vol. 18, no. 2, pp. 461-475, 2016.

[9]

E. Kazamia, D. C. Aldridge and A. G. Smith, "Synthetic ecology - A way forward for sustainable algal biofuel production?," Journal of Biotechnology, vol. 162, pp. 163-169, 2012.

[10]

J. D. Orth, I. Thiele and B. Ø. Palsson, "What is flux balance analysis?," Nature Biotechnology, vol. 28, pp. 245-248, 2010.

[11]

K. Höffner and P. I. Barton, "Design of Microbial Consortia for Industrial Biotechnology," Computer-Aided Chemical Engineering, vol. 34, pp. 65-74, 2014.